Your boiler is currently preparing to start the heating cycle and is warming up the internal fan.

Heating mode fan start-up

What causes this fault?

This code appears when the boiler’s internal computer tells the fan to begin spinning in preparation for a heating cycle. It is a normal part of the ignition process where the fan clears the combustion chamber and ensures a safe flow of air before the gas is lit. If the code stays on screen for a long time, it may suggest the fan is struggling to reach the required speed.